Multiconductor cable harnesses are utilized in a wide variety of applications and are especially advantageous for use in connecting the contacts of remotely located electrical components and/or circuits wherein it is further desired to establish solderless contact engagement of the selectively releasable type which is extremely advantageous for use in apparatus of modularized design to facilitate removal and replacement of the components without the need for soldering and resoldering connections, the latter activities being both tedious and time consuming.
The assembly and testing of multiconductor wire harnesses are, likewise, tedious and time consuming manual activities. As a result, efforts have been made to simplify such procedures. Making reference to U.S. application Ser. No. 968,820, filed Dec. 11, 1978, in the names of William Helms and Jack Adams and assigned to the assignee of the present invention, a review of efforts to facilitate testing and assembly of multiconductor harnesses is set forth. Summarizing these efforts, apparatus has been developed for identifying and displaying the number of a wire in a multiconductor harness selected by an operator to facilitate harness assembly. In the testing field, completed harnesses have been compared in test rigs against known good harnesses by coupling the end connectors of the known good harness in parallel with the harness under test and detecting for the presence of completed circuit loops to establish the correctness of the interconnections for the harness under test. Efforts have also been directed to providing a memory means containing information representative of the known good harness and for comparing the harness under test against the stored data, although these later efforts have been less than successful.
It was not until the advent of the invention described in copending application Ser. No. 968,820 that apparatus became available for testing harnesses at high speed by examining the electrical interconnections of a harness under test, said apparatus incorporating novel scanning and encoding means and means for comparing the data obtained representative of the electrical interconnections with data of a known good harness stored in a high speed random access memory, as well as means for providing visual and/or audible displays to indicate good harnesses and, in the case of defective harnesses, to indicate erroneous connections, the nature of the erroneous connection, and the identity of the erroneous connection points.
Using the above-identified system described in copending application Ser. No. 968,820, which may be characterized as employing a serial scanning technique, tests for continuity between a preselected point and all remaining points of a harness, on a one-at-a-time basis requires several seconds to complete. Efforts to shorten the scanning interval for the above technique have been unsuccessful due to the presence of capacitance between conductors of a harness. The higher the capacitance values, the larger the test current required to provide a current flow for a time interval sufficient to be assured that a conductive path is present.
A scan time of several seconds is unacceptable for advising an assembler of the nature of the last assembled conductor. An upper limit of under two seconds is deemed to be satisfactory for advising an assembler of the verification of correctly connected conductor, or, alternatively, the presence of an incorrectly connected conductor.